Background:Although various clinical tests are utilized to assess lumbar spine instability (LSI), few have documented diagnostic efficacy. We assessed the diagnostic efficacy of four clinical and one radiographic test for LSI in patients with degenerative lumbar disease.

Methods:A cohort of 52 patients with pain attributed to lumbar spine stenosis and degenerative spondylolisthesis were prospectively evaluated utilizing dynamic X-rays, the passive lumbar extension (PLE) test, instability catch sign, painful catch sign, and the apprehension sign. The results of these preoperative tests were compared with spinal surgeons’ intraoperative documentation of spinal instability considered in this study as the “gold” standard.

Lumbar spinal instability (LSI) is a common cause of nonspecific low back pain (LBP).[1] At present, flexion-extension X-rays are the standard method for measuring anteroposterior translation[24] but have several shortcomings.[2] There are several clinical tests for diagnosing LSI,[1235] however, none have been previously proven to be effective measures for LSI.

We investigated the diagnostic efficacy of dynamic X-rays and four clinical tests to assess LSI: (a) passive lumbar extension (PLE) test, (b) instability catch sign, (c) painful catch sign, and (d) apprehension sign utilized to establish the diagnosis of LSI. Furthermore, patients were followed 6 months postoperatively with dynamic X-rays to determine if they became unstable.

Table 1

Comparing the age, gender and duration of symptoms between stable and unstable patients

Imaging assessment

Preoperatively, all patients had dynamic radiographs and MRI [ Table 2 ]. The need for fusion after laminectomy/decompression was based on intraoperative documentation of active translation of >4 mm or rotation of >10 degrees at the level of listhesis. All images were reviewed by three independent specialists: one radiologist, an orthopedic, and a neurological spine surgeon [ Table 3 ]. Prior to surgery, the two spine surgeons used the JOA score and four clinical examinations to confirm LSI: the passive lumbar extension (PLE) test, the instability catch sign, the painful catch sign, and the apprehension sign [ Table 4 ].

Table 2

Comparing the radiographic and intraoperative findings

Table 3

Showing our material briefly

Table 4

Comparing the outcomes of clinical tests and intraoperative findings

Intervention

Patients underwent decompression by the two attending surgeons who could see the images but were not informed of the outcome of the clinical tests. They could independently judge whether patients had LSI and required fusion or not. In addition, patients underwent dynamic X-rays 6 months postoperatively to see if they developed LSI.

Lumbar canal stenosis was present in 35 patients, whereas stenosis/degenerative spondylolisthesis was found in 17. The average age of patients was 56.7 years.

Although preoperative dynamic X-rays showed LSI in 28 patients, 33 patients were unstable intraoperatively (63.5%). The sensitivity, specificity, PPV, NPV, and accuracy of dynamic radiography in establishing the diagnosis of LSI were uniformly high [Tables 3 and 4]. Even though the PLE test had the highest efficacy in diagnosing LSI, there was no significant correlation with neurologic symptoms (P = 0.65) [Table 4].

Intraoperative documentation of LSI best correlated with preoperative dynamic X-ray evidence of instability. Similar to Kasai et al.,[6] our findings confirmed that the PLE test had the highest diagnostic efficacy among all the clinical measures with a sensitivity of 78.8% and specificity of 94.7% [Table 5].

Table 5

Diagnostic efficacy of clinical tests

Limitations

Although two expert spine surgeons evaluated the presence of intraoperative LSI, there may still be nonreproducible intraoperative surgeon-bias constituting a flaw in the study design. Another shortcoming of this study is the relatively low number of cases included.

Preoperative dynamic X-rays best predicated the chance of intraoperative documentation of LSI as performed by two spine surgeons. Among the clinical tests for assessing preoperative LSI, the PLE had the highest predictive value.

1 Comments

Sunil Munakomi

Posted February 8, 2018, 5:04 pm

One of the simple clinical methods for diagnosing underlying lumbar canal stenosis is looking out for the presence of extensor digitorum brevis (EDB) wasting on the lateral aspect of the foot. This is supplied by L5 which is the mostly affected region on degenerative lumbar canal stenosis.This method is reliable with minimal inter-observer bias.